PRESYNAPTIC GAMMA-AMINOBUTYRIC ACID RESPONSES IN THE OLFACTORY CORTEX

Potential changes were recorded from the lateral olfactory tract in slices of rat olfactory cortex in vitro at room temperature. Superfused γ‐aminobutyric acid (GABA) usually produced a dose‐related depolarization of the lateral olfactory tract. Muscimol and 3‐aminopropanesulphonic acid appeared more potent depolarizing agents than GABA, and glycine and taurine appeared less potent. Carbachol and glutamate were virtually ineffective. The GABA responses were at least partially Cl−‐dependent. (+)‐Bicuculline and higher concentrations of strychnine antagonized the GABA but not the glycine‐induced depolarizations. Paradoxically, responses to high doses of GABA were sometimes potentiated by both bicuculline and strychnine. It is suggested that GABA receptors could occur as widely on nerve terminals as they do post‐synaptically in the CNS, where GABA could be involved in the modulation of transmitter output. 1979 British Pharmacological Society